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  1. #include<bits/stdc++.h>
  2. using namespace std;
  3. bool dfs(int s,const vector<vector<int>> &adj,vector<bool> &vis,vector<bool> &stack_n){
  4. 	vis[s]=true;
  5. 	stack_n[s]=true;
  6. 	for(int ngb:adj[s]){
  7. 		if(vis[ngb]==false){
  8. 			if(dfs(ngb,adj,vis,stack_n)){
  9. 				return true;
  10. 				break;
  11. 			}
  12. 		}else{
  13. 			if(stack_n[ngb]=true){
  14. 				return true;
  15. 			}
  16. 		}
  17. 	}
  18. 	stack_n[s]=false;
  19. 	return false;
  20. }
  21. int main(){
  22. 	int v,e;
  23. 	cin>>v>>e;
  24. 	vector<vector<int>> adj(v);
  25. 	for(int i=0;i<e;i++){
  26. 		int a;
  27. 		int b;
  28. 		cin>>a>>b;
  29. 		adj[a].push_back(b);
  30. 	}
  31. 	bool flag=false;
  32. 	vector<bool> vis(v,false);
  33. 	vector<bool> stack_n(v,false);
  34. 	for(int i=0;i<v;i++){
  35. 		if(vis[i]==false){
  36. 			if(dfs(i,adj,vis,stack_n)){
  37. 				flag=true;
  38. 				break;
  39. 			}
  40. 		}
  41. 	}
  42. 	if(flag){
  43. 		cout<<"cycle";
  44. 	}else{
  45. 		cout<<"no cycle";
  46. 	}
  47. }
Success #stdin #stdout 0.01s 5296KB
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stdout
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no cycle
https://ideone.com/JBGZWc
language:
C++ (gcc 8.3)
created:
4 days ago
visibility:
public

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